ANALYSIS OF THE EFFECT OF SHRINKAGE ON MACROSEGREGATION IN ALLOY SOLIDIFICATION

Numerical calculations based on a continuum model are used to examine the effects of solidification shrinkage on the redistribution of solut e in a Pb-19.2 pet Sn mixture which is convectively cooled at a sidewa ll. For each of three different cooling rates, separate calculations a re performed for shrinkage- and buoyancy-induced flows, as well as for the combined influence of shrinkage and buoyancy effects. The calcula tions reveal that flow and macrosegregation patterns are more strongly influenced by buoyancy effects over a wide range of solidification ra tes. Although extremely large solidification rates yield small regions near the chilled wall in which shrinkage-induced flows control the re distribution of solute, the overall effect on macrosegregation is smal l relative to that associated with buoyancy. Scaling analysis of the g overning equations produces reference shrinkage and buoyancy velocitie s which can be used to extend the current numerical results to other b inary systems.